Building a new database for a website...and am curious on what is the best way to generate user_id's. I have a basic table that contains fields: Index, Login_Id, and Password. I plan to use the encrypt function for the password field, what is the best key to use? Maybe the users id?

I had thought maybe something like: Laaa-0000-llll as the format for the id. Where the first character is related to that users last name? Is this a bad idea, I am not partial. I just want it to be robust for a large number of users, and still secure. I do not know much about encryption...

Would a all numeric user id work well? My thought was that an id that contained useful information could aid in search queries...is this feasible?

Any suggestions welcome...